The present invention relates to an image reading apparatus for reading an image of an original placed on an original placement table, and particularly to an image reading apparatus capable of eliminating an influence of outside light.
An image reading apparatus for irradiating an original placed on an original placement table with light from a light source and reading an image of the original based on reflected light reflected by its original has been contemplated conventionally. In this kind of image reading apparatus, when light (the so-called outside light) from the outside of the image reading apparatus enters the periphery of an original, this affects a detection result of the reflected light. Therefore, a proposal to detect the presence or absence of outside light based on a light amount adjusted value obtained at the time when light from a light source is gradually intensified in a state of opposing a light receiving element for detecting the reflected light to a reference member and use a predetermined light amount set value in the case of the presence of the outside light has been made.
In the related art, white level data obtained based on an output of a light receiving element with respect to reflected light reflected by the reference member after being irradiated with light from a light source adjusted by the light amount adjusted value is used as data in which outside light similar to that at the time of acquiring the light amount adjusted value is reflected as it is.